Experiments are in progress designed to evaluate changes in cerebral electrophysiology, problem-solving behavior, and sleep patterns associated with early methadone addiction, continuous dependency, and withdrawal. Electrophysiological changes at various subcortical recording sites and cortical areas are studied by means of averaged evoked potentials and frequency characteristics of on-going EEG activity. Behavioral changes are assessed by performance on selected tasks of the Wisconsin General Testing Apparatus (WGTA) by performance on simple operant tasks under various schedules of reinforcement and by quantitative analyses of spontaneous behaviors recorded via time-lapsed videotape. Examining concurrent electrophysiological and behavioral measures allows stronger inference concerning the effects and possible sites of action of the drug. The specific objectives are to: (1) measure relative responsiveness of the electrical activity of the brain before, during addiction, and at intervals through out sustained drug intake and during withdrawal; (2) investigate the possible site of action of the drug in the brain by noting which systems or areas are most affected as reflected by changes in cerebral electrophysiology of the animals; (3) note the effects of the drug on the animal's behavioral efficiency and on its sleep patterns; (4) study the interaction of methadone with other drugs commonly used by the addict; (5) quantify and describe irreversible changes in electrophysiological and behavioral measures if these occur.